munirsi di biglietto a terra

"Munirsi di biglietto a terra" is a warning message that advise passengers to get the ticket before making the trip/entering the bus.
How can I render it into english in the best way?
Passengers are advised to buy the fare ticket before getting in the bus.
but it is very long..
otherwise, Be advised: tickets are not sold inside the bus.

I agree with Johngiovanni; one of the most remarkable differences between Italian and English, in my opinion, is the use of personal/impersonal forms: we use impersonal forms very often in these contexts, whereas English people are more used to address to an ideal "you".